Actors not credited on-screen

[MacLeod]

Because they stand out from the rest of the list and get more attention. Also, they usually go at the end of the list, and people are most likely to notice the first and last items on a list.

As I understand it, the practice grew out of Jonathan Harris's situation on Lost in Space. He was added to the cast after the pilot, but all the other cast members' credit order was already set by contract, so he had to go last, but it would've been ignominious for an experienced adult actor to be billed after two children. So to compensate, they credited him as "Special Guest Star" for extra attention/prestige.

These days, it's become fairly standardized that an "And Actor as Character" credit at the end is second only to lead billing in prominence/pay. When Michael Shanks left Stargate SG-1 and later came back, they couldn't give him back his original second billing because it would mean demoting the other regulars, so instead they gave him an "And/as" credit at the end, which was pretty much comparable to second billing.

You can see a similar think in SG:A when Paul McGillion was added to the main cast in season 2 he got With/as credit along with David Hewlett who also got an and/as credit.

 

[Ensign Seven]

Armin Shimerman also got an "and/as" in Caretaker.

Following the insights of this thread and coming back to my question in the first post, my theory now is that Scott Jaeck simply did not want to be credited for the role. The actors of Stadi and the unnamed doctor were only credited as "Co-stars"; there is nothing to assume that it would have been different for Cavit. The extent or difficulty of the role might not have justified more than "Co-star" and maybe that was not enough for him. During my little research I found out that some consultants discourage actors from having too many "Co-star" credits under ones belt since they are the lowest level and too many of them might hinder further career chances. So if you cannot be a "Guest star", then better cash in, but go uncredited.

 

[Mr. Laser Beam]

my theory now is that Scott Jaeck simply did not want to be credited for the role.

Since Cavit was such a dumbass (yeah, let's start running across the bridge right in the middle of an attack, WHAT COULD POSSIBLY GO WRONG?), that's understandable.

 

[johnnybear]

Not exactly. DS9 couldn't afford to pay Frank Langella's salary, but he really wanted to do the show. Since accepting a lower salary could have potentially have ruined leverage for him in any future negotiations, he went uncredited. Meaning that in a very strict legal sense, he didn't technically do the role, allowing him to do the role he wanted to without losing leverage in future negotiations. The acting profession has weird loopholes.

I always thought Frank Langella was credited for parts one and two but strangely not for episode three so I assumed at first he wasn't in the last part, but he was, briefly as I remember!
JB

 

[Tracy Trek]

With Whoopi Goldberg, she chose to "waive billing" in "Star Trek Generations" because it was her friend Patrick Stewart's first time as a feature film lead actor, but Whoopi's previous Academy Award Winner status would normally mean that she should get billed over him, and she didn't want to overshadow her friend.

Whoopi does get billed in "Nemesis", but it's more of a cameo.

I was going to ask about this. So thanks for mentioning it.

I had thought it was something like that. But sometimes in cases like that, I think I've seen where a guest actor will have a special credit in the opening credits near the end after all the other actors names are given.

 

[Therin of Andor]

I think I've seen where a guest actor will have a special credit in the opening credits near the end after all the other actors names are given.

Those are negotiated by the actors' agents, in addition to salary. Diana Muldaur and Whoopi Goldberg in "Star Trek: The Next Generation", Jonathan Harris in "Lost in Space" and "Presenting Persis Khambatta" for "Star Trek: The Motion Picture" (rather than "Introducing...", because she had already made films in India).